His elder sister Joy became an English teacher at Claverham Community College in Battle, East Sussex, and younger brother Leon (1927–2015) became an actor.

Offered a professional acting part by the Brighton impresario Charles F. Smith, he made his first professional appearance in January 1942, playing Dudley in a production of George and Margaret for the Mobile Entertainments Southern Area company (known as MESA) and in other modern comedies, playing to the armed forces all along the South Coast of England during the Second World War[6] and later trained as an actor for two terms[7] at the Webber Douglas Academy of Dramatic Art.

[9] After the critical and financial success of his first screen leading role in The Cruel Sea (1953), made by Ealing Studios, in which he co-starred and received top-billing with Jack Hawkins, Sinden was contracted for seven years to the Rank Organisation at Pinewood Studios and subsequently had prominent roles in 23 movies during the 1950s and early 1960s, including Mogambo; Doctor in the House; Above Us the Waves; The Black Tent; Eyewitness; Doctor at Large; The Siege of Sidney Street and Twice Round the Daffodils.

[10] Sinden became associated with his character of "Benskin" in the Doctor film series as the duffel-coated medical student, regularly failing his finals and spending most of his time chasing pretty nurses, accompanied by his trade-mark "wolf-growl".

[12] In 1956, a profile was written on him which stated:In the three years since his début in The Cruel Sea, the un-temperamental Sinden has moved steadily up the British film ladder until people are noticing, not without surprise, that he is suddenly one of the country's prime box-office favourites.

He is not colourful or flamboyant, yet he has his niche in public favour, as a recent poll proved: British women-folk voted him "The face we'd most like to see across our breakfast table."

His other notable leading performances in the commercial theatre included roles in productions such as There's a Girl in My Soup (1966); In Praise of Love (1973); An Enemy of the People (1975); Present Laughter (1981); The School for Scandal (1983); The Scarlet Pimpernel (1985); Major Barbara (1988); Diversions and Delights (one-man show as Oscar Wilde, 1989); She Stoops to Conquer (1993); That Good Night (1996) and Quartet (1999).

Outstanding among his many stage appearances for the RSC, both at Stratford-upon-Avon and in London's West End (usually at the Aldwych Theatre), was his performance in 1963 as the Duke of York in The Wars of the Roses opposite Peggy Ashcroft as Queen Margaret.

[22] For the 1976 Stratford season and then at the Aldwych Theatre in 1977, Sinden won the Evening Standard Award as Best Actor for his performance in the title role of King Lear (with Michael Williams as the Fool).

[25][26] At the same time he was also rehearsing the third season of the LWT sitcom Two's Company with Elaine Stritch during the daytime and filming the show at the studio in front of a live audience on Sunday evenings.

[a] Everyman editor and critic Gareth Lloyd Evans observed that his interpretation was "not…about colour or racialism" but one that illuminated the character's personal tragedy.

"[32] The Daily Telegraph's review states: "Great West End Theatres is a lovely documentary series, made by the director Marc Sinden.

In 1978, Sinden was the leading guest star in the first "special" of Thames Television's The Morecambe & Wise Show, in which he carried on the butler's role.

In 1979, Sinden presented a documentary series on BBC2 (later repeated in 1981 on BBC1), Discovering English Churches inspired by his grandfather's architectural drawings and watercolours.

[citation needed] Sinden was regularly spoofed on Spitting Image, the 1980s British satirical television programme in which famous people were lampooned by caricatured latex puppets.

[42] In reply to a question from an audience member during a performance at the Yvonne Arnaud Theatre of An Evening with... Sir Donald Sinden, he said he had worked out that, apart from "gaps before the next job started", he had only had a total of five weeks' unemployment between 1942 and 2008.

[44] On 9 October 2012, he celebrated his 89th birthday and his retirement after 30 years as the longest-standing president of the Royal Theatrical Fund (founded by Charles Dickens in 1839) with a celebratory lunch for 350 guests at the Park Lane Hotel, London; this was compered by Russ Abbott, and the subsequent charity auction was conducted by Jeffrey Archer.

Leading the tributes was Jean Kent, who had co-starred with Sinden in Bernard Delfont's 1951 stage production of Froufrou; letters from Queen Elizabeth II and Prince Albert of Monaco were read out, and speeches given by Julian Fellowes, Ray Cooney and Gyles Brandreth.

[52] According to his second autobiography, while investigating his family genealogy he discovered that the only previous relatives who were also members of the theatrical profession were the Victorian brother and sister act of Bert and Topsy Sinden, who were distant cousins.

"[51] Sinden died at his home in Wittersham on the Isle of Oxney, Kent, on 12 September 2014, aged 90, from prostate cancer diagnosed several years earlier.

[53][54] Speaking at his funeral, held on 19 September at St John the Baptist Church, Wittersham, were his grandson Hal Sinden, Dame Judi Dench and Sir Patrick Stewart.